1. Field of the Invention
The present invention relates to charge and discharge control in a power supply system including a plurality of power storage devices.
2. Description of the Background Art
A hybrid vehicle capable of running using at least one of an internal combustion engine and a motor that operates upon receiving electric power from a rechargeable power storage device, in which the power storage device is chargeable by a power generation device generating electric power by using outputs from the internal combustion engine, has been known. Among such hybrid vehicles, a vehicle that can run by switching between a running mode in which the vehicle mainly runs only with a motor by using electric power stored in the power storage device for running without maintaining the same (referred to as a “CD (Charge Depleting) mode,” an “EV (Electric Vehicle) mode” or the like, and hereinafter referred to as the “CD mode”) and a running mode in which the vehicle runs while maintaining electric power stored in the power storage device at a prescribed target (referred to as a “CS (Charge Sustaining) mode,” an “HV (Hybrid Vehicle) mode” or the like, and hereinafter also referred to as the “CS mode”) has also been known.
Regarding a power supply system mounted on such a hybrid vehicle, Japanese Patent Laying-Open No. 2008-109840 discloses a power supply system including a plurality of power storage devices. In this power supply system, a remaining electric power amount down to SOC at which allowable discharge electric power that can be output from the power storage device is to be restricted is calculated for each power storage device, and a discharge allocation ratio of the power storage device is calculated in accordance with a ratio of the remaining electric power amount. In addition, a charge acceptable amount up to SOC at which acceptable charge electric power that can be input to the power storage device is to be restricted is calculated for each power storage device, and a charge allocation ratio of the power storage device is calculated in accordance with a ratio of the charge acceptable amount. When electric power is supplied from the power supply system to a drive force generation portion, each converter is controlled in accordance with the discharge allocation ratio, and when electric power is supplied from the drive force generation portion to the power supply system, each converter is controlled in accordance with the charge allocation ratio.
According to this power supply system, even when charge and discharge characteristics of a plurality of power storage devices are different among them, performance of the system can be exhibited to its maximum.
As a method of managing electric power is different between a case where a running mode is set to the CD mode and a case where a running mode is set to the CS mode as described above, it is necessary to appropriately manage electric power in accordance with the running mode. If this electric power management is inappropriate, any power storage device among the plurality of power storage devices reaches discharge limit or charge limit earlier than other power storage devices and thereafter maximum discharge characteristics or charge characteristics as the whole power supply system cannot be obtained. Japanese Patent Laying-Open No. 2008-109840 above fails to address a method of managing electric power in accordance with the running mode (CD mode/CS mode).